The major objective of this proposal is to investigate the etiology and pathogenesis of Kawasaki Syndrome (mucocutaneous lymph node syndrome). Kawasaki Syndrome, a recognizable acute febrile exanthematous disease of childhood, has been recognized with increasing frequency outside Japan since its first description in the United States in 1974. Two percent of cases die of sudden death from coronary artery disease. Pathologically the Syndrome consists of acute inflammatory arteritis involving musculoelastic arteries with special prediliction for the coronary arteries and is indistinguishable from infantile periarteritis nodosa. No clues to etiology, pathogenesis or effective therapy have emerged. We propose a prospective clinical follow-up study of Kawasaki Syndrome in Hawaii, the area of the United States where the Syndrome was first recognized and is most prevalent. A search for the participation of infectious agents in the disease will be made by the tissue culture, animal inoculation and electron microscopy of acute specimens. Immunologic studies will include serial determinations of IgE and complement components. Serum immune complexes will be searched for by C1Q binding, Raji cell and cold insoluble complex assays. HLA typing will be performed because of the genetic predisposition noted in Japanese patients. Fluorescent antibody methods will be used to search for participation of immunoglobulins, complement and specific antigens in arterial lesions found at autopsy or by biopsy. Case-control epidemiologic study will be performed.